Thanks for your comment Oli.
I found out that my input (particles.star) has merely 90 lines.
Now, I manually picked 2k particles by relion_GUI. I will extract, semi-autopick and fullly auto-pick to finally pick 30~40k particles. I am excited to see how this will work in cryosparc.
I read that 2D classification may not be necessary (Advice for Classification), so I will skip for now.